Field of the Invention
The present invention is generally related to vision correction systems. In one embodiment, the invention provides systems and methods for verifying a refractive surgical procedure, ideally by ablating a customized corrective lens before imposing a corresponding refractive correction in the corneal tissues.
Known laser eye procedures generally employ an ultraviolet or infrared laser to remove a microscopic layer of stromal tissue from the cornea of the eye to alter the refractive characteristics of the eye. The laser removes a selected shape of the corneal tissue, often to correct refractive errors of the eye. Ultraviolet laser ablation results in photodecomposition of the corneal tissue, but generally does not cause significant thermal damage to adjacent and underlying tissues of the eye. The irradiated molecules are broken into smaller volatile fragments photochemically, directly breaking the intermolecular bonds.
Laser ablation procedures can remove the targeted stroma of the cornea to change the cornea""s contour for varying purposes, such as for correcting myopia, hyperopia, astigmatism, and the like. Control over the distribution of ablation energy across the cornea may be provided by a variety of systems and methods, including the use of ablatable masks, fixed and moveable apertures, controlled scanning systems, eye movement tracking mechanisms, and the like. In known systems, the laser beam often comprises a series of discrete pulses of laser light energy, with the total shape and amount of tissue removed being determined by the shape, size, location, and/or number of a pattern of laser energy pulses impinging on the cornea. A variety of algorithms may be used to calculate the pattern of laser pulses used to reshape the cornea so as to correct a refractive error of the eye. Known systems make use of a variety of forms of lasers and/or laser energy to effect the correction, including infrared lasers, ultraviolet lasers, femtosecond lasers, wavelength multiplied solid-state lasers, and the like. Alternative vision correction techniques make use of radial incisions in the cornea, intraocular lenses, removable corneal support structures, thermal shaping, and the like.
Known corneal correction treatment methods have generally been successful in correcting standard vision errors, such as myopia, hyperopia, astigmatism, and the like. However, as with all successes, still further improvements would be desirable. Toward that end, wavefront measurement systems are now available to measure the refractive characteristics of a particular patient""s eye. By customizing an ablation pattern based on wavefront measurements, it may be possible to correct minor refractive errors so as to reliably and repeatably provide visual accuities greater than 20/20. Alternatively, it may be desirable to correct aberrations of the eye that reduce visual acuity to less than 20/20. Unfortunately, these measurement systems are not immune from measurement error. Similarly, the calculation of the ablation profile, the transfer of information from the measurement system to the ablation system, and the operation of the ablation system all provide opportunities for the introduction of errors, so that the actual visual accuities provided by real-world wavefront-based correction systems may not be as good as might be theoretically possible.
In light of the above, it would be desirable to provide improved vision correction systems and methods.
In a first aspect, the present invention provides a method comprising measuring an actual optical error of an eye. A plan is generated for a corrective procedure of the eye from the measured optical error. A verification lens is formed based on the measured optical error to verify the procedure plan.
Optionally, irregular optical error of the eye can be measured so that the verification lens compensates for the irregular error. In many embodiments, a wavefront of light passing through the optical components of the eye will be measured with a wavefront sensor to measure the refractive error of the eye. The verification lens can be generated by ablating a lens material according to an ablation pattern.
The ablation pattern for the verification lens can be calculated from the measured optical error of the eye, and from characteristics of the lens material, such as a refractive index of the lens material, a rate of ablation of the lens material, and/or a shape of ablation of the lens material (for example, the propensity of the lens material to differ in ablation depth across a uniform ablation energy beam, such as any xe2x80x9ccentral islandxe2x80x9d properties of the lens material). A corneal tissue of the eye may be ablated according to an ablation pattern, and the ablation pattern may similarly be calculated based on the measured optical error of the eye and on the corneal tissue characteristics, such as a refractive index of the corneal tissue, a rate of ablation of the corneal tissue, and/or a shape of ablation of the corneal tissue.
In another aspect, the invention also provides a method comprising measuring an actual optical error of an eye of a patient with a wavefront sensor, and also measuring a pupil size of the eye. An ablation pattern is generated from the measured optical error, and an ablation pattern is also generated for lens material, the lens material pattern corresponding to the ablation pattern for the eye. The lens material is positioned relative to an ablation system by aligning indicia of the lens material with a reticule of the ablation system. A verification lens is ablated in the aligned lens material with the ablation system according to the lens pattern. An aperture is aligned with the verification lens, with the aperture size selected in response to the pupil size of the eye. The verification lens and the aperture are mounted to the patient so that the eye is aligned with the verification lens, and an eye chart is viewed with the eye through the verification lens and the aperture to determining whether a corrected visual acuity of the eye is within an acceptable range so as to verify the ablation pattern of the eye.
In other aspects, the invention also provides related systems for verifying and/or correcting optical errors of an eye.